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<h1>Oxygen, O<sub>2</sub></h1>

Oxygen (O<sub>2</sub>) is a diatomic molecule that constitutes about 20.8% of Earth's atmosphere. It is essential for the respiration of most life forms and is a key player in combustion processes. In its liquid and solid states, oxygen is pale blue. Optically, oxygen is generally transparent in the visible region, but it can have strong absorption bands in the ultraviolet and infrared wavelengths. This absorption is vital for protecting life on Earth by filtering out the sun's harmful ultraviolet radiation in the upper atmosphere. In advanced optical applications, oxygen plays a role in the formation of certain oxide materials used in optics, like optical fibers and waveguides. Additionally, pure oxygen environments are sometimes used in various laser processes due to its reactive nature.

<h2>External links</h2>
<ul>
<li><a href="https://en.wikipedia.org/wiki/Oxygen">Oxygen - Wikipedia</a></li>
<li><a href="https://www.webelements.com/oxygen/">Oxygen - WebElements</a></li>
<li><a href="https://webbook.nist.gov/cgi/cbook.cgi?ID=C7782447">Oxygen - NIST Chemistry WebBook</a></li>
</ul>
